This Instructional Activity is a part of the Lesson 2, Unit 3, Grade 7. Students connect the strategy of using the additive inverse to represent a subtraction problem as a sum and using the multiplicative inverse to represent a division problem as a product so that the associative and commutative properties can then be used. Why do we convert differences into sums using opposites? The commutative and associative properties do not apply to subtraction; therefore, we convert differences to sums of the opposites so that we can use the any order, any grouping property with addition. We have seen that the any order, any grouping property can be used with addition or with multiplication.